Our research goals for the coming year include: 1) continuing development of our stereochemical studies involving chiral phosphorothioate substrates and phosphodiesterases, including that from bovine intestine, spleen, and eventually restriction enzymes, in order to determine the overall stereochemistry of the phosphoryl transfer reaction catalyzed by these enzymes; 2) to examine in detail the interesting exchange of O18 out of inorganic phosphate catalyzed by FBPase in the presence of fructose-6-phosphate; 3) construction of the free energy reaction coordinate diagram for FBPase utilizing stopped-flow studies based on a pH indicator method and the aforementioned O18 exchange; and 4) modification of fructose bisphosphatase with active-site reagents in order to establish the nature of the critical amino acid residues involved in the catalysis.